pvt.cppan is a utility CPPAN account and
pvt.cppan.demo contains many projects, but they're not official. You could use them as a starting point in uploading your packages. And official packages will be in
pvt.your_name.* namespace. Also for orgs:
Where does cppan download/generate stuff?
By default, in your user home directory. Like
$HOME/.cppan/storage on *nix or
%USERPROFILE%/.cppan/storage on Windows.
How to change that directory?